Proton Implantation–Induced Reduction of SSF Width and Associated Adverse Effects in 4H-SiC Epitaxial Layers

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Abstract:

Proton implantation has been reported as an effective approach for suppressing bipolar degradation in 4H-SiC; however, implantation inevitably introduces lattice damage and point defects. In this work, we investigate: (i) suppression of Shockley-type stacking fault (SSF) expansion in both the proton-implanted layer and the region beyond the implanted layer, and (ii) adverse effects associated with proton implantation. Half of an n-type 4H-SiC epitaxial wafer was implanted with protons (350 keV, 1×10¹³ cm⁻²) and annealed at 1600 °C for 30 min for dopant activation with carbon capping. SSF expansion was induced by UV laser irradiation, and photoluminescence (PL) imaging was used to quantify SSF width and observe cross sections. The proton-implanted region exhibited clearly reduced SSF expansion, with the expanded SSF width typically about 30 μm smaller than that in the non-implanted region; cross-sectional PL further confirmed that SSFs did not propagate into the near-surface implanted layer. Additional experiments with varied implantation depth and dose revealed a linear relationship between SSF width and active drift-layer thickness (defined as the drift-layer thickness minus the proton implantation depth), consistent with geometric expectations from the wafer off-cut. However, PL observations also showed anomalous SSF morphologies and evidence of dislocations, indicating that proton implantation can generate new SSF nucleation sites. Furthermore, the band-to-band PL peak intensity decreased after implantation and did not recover after the activation anneal, suggesting persistent lattice damage, including in proton-traversed regions. These results highlight a trade-off between SSF-suppression benefits and implantation-induced degradation.

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